1. Field of the Invention
The invention generally relates to a music box. More particularly, the invention relates to a reinforced music box.
2. Description of the Prior Art
Please see FIGS. 1 and 2, which illustrate a conventional music box. The music box comprises a base portion 1, a two-sided cogwheel 2, a step type cogwheel 3, a friction set 4 and a cover portion 5. The two-sided cogwheel 2 and step type cogwheel 3 are disposed in slots provided on the base portion 1 and they are arranged in a parallel manner. They may engage with each. Also, the step type cogwheel 3 engages with a cogwheel set 6 disposed on the base portion 1. The cogwheel set 6 engages with the two-sided cogwheel 2. The cover portion 5 can limit the range of motion of the step type cogwheel 3, two-sided cogwheel 2 and friction set 4. Such music box has the following disadvantages:    (1) Because the thin and fragile spirally cogged stick is not protected, it may be easily damaged or deformed during the assembly or delivery.    (2) Because the cover portion 5 is made of plastic, the motion of the step type cogwheel 3 and cogwheel set 6 produces an upward force, which may cause the cover portion 5 to deform. The deformation may affect the normal range of motion of the step type cogwheel 3.
Please refer to FIGS. 3 and 4, which illustrate another type of conventional music box. A supporting portion 92 is additionally provided and is disposed on top of the base portion 91. The supporting portion 92 is made by an iron plate. A two-sided cogwheel 93 and a step type cogwheel 94 are made of polyformaldehyde (POM). In assembly, the two-sided cogwheel 93 and step type cogwheel 94 are fitted on top of a rack 921 of the supporting portion 92 and they are arranged in a parallel manner. Then stamping is used to connect them. Such music box has the following disadvantages:    (1) Because the supporting portion 92 is made by an iron plate, the stamping would give it rough edges. These rough edges may affect the normal range of motion of the two-sided cogwheel 93 and step type cogwheel 94 and may even accelerate the wear of the cogwheels.    (2) Because the supporting portion 92 has to undergo galvanization, the galvanization may easily cause it to deform. This deformation may affect the precision in assembly for the two-sided cogwheel 93 and step type cogwheel 94 (may even cause difficulty in assembly).    (3) Because pressing is used for the rack 921 of the supporting portion 92, the result of the pressing is often either to tight or too loose. Such result adversely affects the overall structure and the transmission between the cogwheels.    (4) A friction board 96 is additionally provided on the supporting portion 92. Because pressing is needed to connect the friction board 96 with the supporting portion 92, which is made of iron, hence labor cost is enhanced.
From the above, we can see that improvements are needed for the conventional music boxes in terms of material cost, manufacturing process, labor cost and the precision in assembly.